The hydroxyarylsulfonium chlorides form a known class of compounds. These compounds are useful, for example, as surface active agents, biological toxicants, intermediates in the synthesis of organic derivatives, etc. The hydroxyarylpolymethylenesulfonium chlorides are particularly useful as intermediates to the preparation of the corresponding cyclic sulfonium zwitterions (which are water-soluble monomers).
Several methods have been previously used to prepare the hydroxyarylsulfonium chlorides.
U.S. Pat. No. 3,133,971 teaches, for example, that the hydroxyarylsulfonium chlorides can be prepared by reacting a sulfide (R--S--R') with a monophenol in the presence of chlorine at a reaction temperature of from about -50.degree. to about 10.degree. C. The patentee states that the reaction may optionally be conducted in a diluent, such as HCl, concentrated hydrochloric acid, phosphoric acid, alkyl halides, aromatic hydrocarbons, etc. This procedure is plagued, however, by side reactions involving chlorine and phenol which produce undesirable byproducts that are difficult to separate from the desired hydroxyarylsulfonium chloride.
U.S. Pat. No. 3,259,660 teaches a modification of the above reaction. The modification comprises conducting the reaction in two steps. In the first step, chlorine is added to the organic sulfide in a suitable diluent at a reaction temperature of between about -50.degree. and about 10.degree. C thus forming a chlorine complex with the organic sulfide. In the second step, the chlorine complex is added to the monophenol in the presence of a liquid diluent and the reaction mixture reacted under agitation at a temperature of from about -50.degree. to about 20.degree. C until the product is formed. Patentee states that this process is not particularly adaptable to reactions involving highly substituted phenols which may be sterically hindered.
U.S. Pat. Nos. 3,732,317; 3,772,391 and 3,775,485 likewise teach a two step process involving a chlorine complex with the sulfide. In these patents, an organic sulfide (R--S--R') is reacted with chlorine in the presence of sulfuric acid to form a chloro-sulfonium bisulfate of the formula (R--S(Cl)--R').sup..sym. HSO.sub.4.sup..crclbar.. The chloro-sulfonium bisulfate is then reacted with the monophenol to give the corresponding hydroxyarylsulfonium compound.
All of the above patents are limited to the reaction of monophenols with sulfides of the formula R--S--R'. Cyclic sulfides have been consistently omitted from the teachings of these patents.
The reaction of cyclic sulfides with a polyphenol is described, for example, in U.S. Pat. No. 3,767,622. There, patentee teaches that the poly(hydroxyarylpolymethylenesulfonium) salts can be formed in one of two methods. The first method involves reacting a polyphenol with a cyclic sulfide in the presence of chlorine at a temperature of from -40.degree. to -8.degree. C. The product yield from this process is said to be improved by adding anhydrous HCl to the cyclic sulfide prior to adding the polyphenol and chlorine. In the second process, a polyphenol and a polymethylenesulfoxide are condensed in the presence of a strong anhydrous acid, such as HCl. Low temperatures and Lewis acid catalysts (e.g. aluminum chloride, sulfur dioxide, etc.) are said to be useful in minimizing side reactions and improving the color.